The Zoo in Your Poo

From the climb of Ed Yong’s microbial treatise “I Contain Multitudes: The Microbes Within Us and a Grander View of Life” on the The New York Times’ best-seller list to a marked uptick in kombucha consumption, gut health has seen an increased hype in popular culture over the past few years.

While the public has taken interest in the secret lives of their bowels, researchers like School of Medicine immunobiologist Noah Palm GRD ’11 have worked for years to understand the trillions of microbes living inside our guts.

Palm studies how gut bacteria — or the microbiome — can influence health. Specifically, his lab at Yale focuses on how the microbiome interacts with the immune system and how this relationship influences disorders such as inflammatory bowel disease and autism. While researchers have garnered a greater understanding of the microbiome over the past few decades, Palm said that scientists are still working to understand what the optimal microbiome composition looks like.

“We still don’t really have an answer to what a healthy microbiome is,” Palm said.

According to Palm, modern microbiome research has been ongoing for about 20 years. Scientists know that no two guts are the same: Each person has a different composition of up to 1,000 bacterial strains, the balance of which is constantly influenced by factors such as diet, stress and sleep.

Yet, when it comes to what factors make a gut “healthy,” researchers are still stumped. Though studies have uncovered signatures of compromised microbiomes within sick patients, the closest scientists have gotten to an answer is that a healthy gut has “the absence of those signatures,” Palm said.

As public interest in the gut increases — and studies continue to show evidence for the microbiome influencing immunity and mental health — Palm cautioned that scientists are far from developing new microbiome-based therapies to treat or cure certain diseases.

“The microbiome has really captured the public’s imagination in a way that most other aspects of science haven’t,” he said. “That’s a really good thing in some ways, but it’s also dangerous in other ways because it can create a kind of aura of hype.”

Walk into any drug store and a selection of probiotics await, promising to provide a dose of “good” bacteria to naturally bolster gut health. But probiotics — like all dietary supplements — are not tightly regulated by the U.S. Food and Drug Administration. In fact, Palm said that some of his colleagues have tested drugstore probiotics and found that they did not contain the bacteria listed on the label.

Other probiotic research is just as grim: Most groups have found either neutral or negative effects of probiotics on the body, according to Palm. One study from Houston’s MD Anderson Cancer Center and the Parker Institute for Cancer Immunotherapy looked at the effect of probiotics on the immune system, and found that cancer patients taking these supplements were less likely to respond to immunotherapy.

“We wanted to bring this to the forefront of people’s minds: That probiotics sold over the counter aren’t necessary,” Jennifer Wargo, MD Anderson surgical oncologist and the study’s first author, told the health news outlet STAT. “They may not help you, and might even harm you.”

For those looking to bolster their microbiome, Palm said that traditional guidelines for maintaining health — a balanced diet, plenty of exercise and adequate sleep — are the best bets for keeping your gut functioning well. But beyond those suggestions? Scientists have yet to come up with definitive recommendations for the public.